Sumitra, who has two other sons Lalit, 17, and Surendra, 11, as well as daughter Manisha, 14, added: "His things are scattered everywhere. Our house is filled with his belongings.

"Nobody thought this day would come. He was fine. He even said: ‘I’m absolutely fine Mum’. His voice echoes in my ear. The way he used to call me. I am devastated. I feel everything is over."

Mahendra hit the headlines with his extraordinary condition last year.

His story touched the heart of mother of two Julie Jones, from Liverpool, who went on to raise £12,000 for Mahendra to have life changing surgery.

A documentary, The Boy Who Sees Upside Down, was aired on Channel 5 Extraordinary People series in May this year.

It followed Mahendra’s remarkable journey, seeing him endure a ten-hour operation to remove disks from his neck and replace them with bone graft from his pelvis, before a metal plate was fitted in his neck to secure it straight.

Dr Krishnan, from Apollo Hospital, in Delhi, who had worked for the NHS for 15 years before returning to India to help extreme spinal disorders, was amazed by Mahendra’s speedy recovery and had been overjoyed at the way his neck had healed.

Mahendra Ahirwar was able to attend school following his operation (Image: Cover Asia Press/Faisal Magray)

He insisted that his death was not related to his recent operation, adding: "Mahendra's death is not a complication of the surgery or any other intervention.

"If that was the case, he would have died on the operating table or in ICU, not eight months later.

"I think his lifespan was limited irrespective of anything else but at least he had several months of being able to see upright.

"The most common cause of death in congenital myopathy is from cardiopulmonary complications.

"There are so many types of congenital myopathy and many subtypes that it's impossible to identify which one Mahendra had and the prognosis in terms of life expectancy.